Is the heighth of the RE040 tire roughly proportional to how much life the tire has left? How can I tell how many miles are left?

 

Since the difference between new and worn tires is about 10/32” the answer is no. Also miles don't mean much as members here have gotten 12,000-25,000 on the same brand of tires. Tires have built in wear bars that run across the tread. When this bar of rubber is totally visible across the face of the tire it’s time to replace. You can also purchase for less than $10.00 a gauge designed to measure tread depth at any auto parts store, 2/32” is the lowest recommended depth. Here is a link with more info
http://www.tirerack.com/tires/tirete...eplacewhen.jsp